A high amount of dietary fat has been implicated in the development of several diseases (Owen et al., 2000c). Atherosclerosis (Kuller, 1997) and coronary heart disease (Gerber, 1994), as well as cancer of the breast (La Vecchia et al., 1998), prostate (Chan et al., 1998), ovary (Risch et al., 1994), and colon (Armstrong and Doll, 1975) have each been associated with elevated dietary fat. However, evidence indicates that it is not only the amount, but also the type of dietary fat that is important in the etiology of some cancers (Bartsch et al., 1999).
Olive oil, the principal fat component of the Mediterranean diet, has been associated with a lower incidence of coronary heart disease (Owen et al., 2000b; Parthasarathy et al., 1990; Mattson and Grundy, 1985) and certain cancers (d'Amicis and Farchi, 1999; Braga et al., 1998; Martin-Moreno et al., 1994). Several laboratories have reported that the hydrolysis of the olive oil phenolics oleuropin and other family members lead to small phenolic components with strong chemoprotective activity (Owen et al., 2000a; Manna et al., 2000). In particular, the olive oil phenolic hydroxytyrosol prevents low density lipoprotein (LDL) oxidation (Visioli and Galli, 1998), platelet aggregation (Petroni et al., 1995), and inhibits 5- and 12-lipoxygenases (de la Puerta et al., 1999; Kohyama et al., 1997). Hydroxytyrosol has also been found to exert an inhibitory effect on peroxynitrite dependent DNA base modification and tyrosine nitration (Deiana et al., 1999), and it counteracts cytotoxicity induced by reactive oxygen species in various human cellular systems (Manna et al., 2000). Finally, studies have shown that hydroxytyrosol is dose-dependently absorbed in humans following ingestion, indicating its bioavailability (Visioli et al., 2000).
Conventionally, olive oil production involves crushing olives, including the pits, to produce a thick paste. During this procedure, the crushed olives are continuously washed with water, a process known as “malaxation.” The paste is then mechanically pressed to squeeze out the oil content. In addition to providing olive oil, the pressing also squeezes out the paste's water content. Such washing and pressing steps yield a considerable amount of water, referred to as “vegetation water.”
Both the pit and the pulp of olives are rich in water-soluble, phenolic compounds. Such compounds are extracted from olives during malaxation, according to their partition coefficients, and end up in the vegetation water. This explains why various phenolic compounds, such as oleuropein and its derivatives, produced in olive pulp, can be found in abundance in vegetation waters. Similarly, a number of monophenolic compounds, such as tyrosol and its derivatives, produced in olive pits, are also abundant in vegetation waters.
Because of the strong chemoprotective activity of hydroxytyrosol, it is desirable to develop a method which produces an aqueous olive extract with a high percentage of hydroxytyrosol.